1. Field of the invention
The present invention concerns an articulated device applicable in particular to the pointing of a directional antenna of a satellite.
The invention is also directed to a telecommunication satellite, in particular a data relay satellite, equipped with an articulated device of this kind.
The invention is also directed to an antenna pointing method using an articulated device of this kind.
2. Description of the prior art
Telecommunication satellites in general and data relay satellites in particular generally have parabolic antennas that are directional and which must be isolated from movements of the satellite during attitude and orbit correction maneuvers. In the case of data relay, it is necessary to direct the antenna towards mobile targets on the earth or in low orbit around the earth. These isolation and pointing functions are routinely implemented by a mechanism with two degrees of freedom referred to hereinafter as an antenna pointing mechanism.
There are two known ways to point the beam of a transmit antenna installed on a satellite. As an antenna primarily comprises at least one feed, a reflector and a support structure for these members, the first way is to point the antenna as a whole, that is to say the feed, the reflector and the support structure. The second way is to move only the reflector, so as to point the radiation from the feed reflected by the reflector.
The first solution has the disadvantages of a large mass, a large volume and a large inertia to be displaced and also requires radio frequency signals to be guided through the antenna pointing mechanism, which can be complex to achieve. The second solution is simpler and used more often but it leads to distortion of the radiation pattern of the antenna because of modification of the relative positions of the feed and the reflector. The feed does not remain at the focus of the antenna reflector.
An object of the present invention is to solve these problems and to propose a new pointing mechanism, adapted in particular to point a satellite antenna, which is of the articulated device type and provides at least two possibilities of rotation about a virtual rotation center remote from the articulated device, without alteration to the geometry of the antenna.